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Rutkoski CF, Grott SC, Israel NG, Guerreiro FDC, Carneiro FE, Bitschinski D, Warsneski A, Horn PA, Lima D, Bastolla CLV, Mattos JJ, Bainy ACD, da Silva EB, de Albuquerque CAC, Alves TC, de Almeida EA. Prednisone and prednisolone effects on development, blood, biochemical and histopathological markers of Aquarana catesbeianus tadpoles. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2024; 268:106869. [PMID: 38387247 DOI: 10.1016/j.aquatox.2024.106869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 01/31/2024] [Accepted: 02/17/2024] [Indexed: 02/24/2024]
Abstract
Synthetic glucocorticoids are often found in surface waters and can cause harmful effects to aquatic organisms such as amphibians. In this work we evaluated the effects of the drugs prednisone (PD) and prednisolone (PL) on developmental, molecular, blood, biochemical and histological markers. Aquarana catesbeianus tadpoles were exposed for 16 days to environmentally relevant concentrations of 0, 0.1, 1 and 10 µg/L of both drugs. PD increased the transcript levels of the enzyme deiodinase III (Dio3), the hormones cortisol and T4 and delayed development. Changes in the thyroid gland occurred after tadpoles were exposed to both drugs, with a reduction in the diameter and number of follicles and an increase/or decrease in area. Also, both drugs caused a decrease in lymphocytes (L) and an increase in neutrophils (N), thrombocytes, the N:L ratio and lobed and notched erythrocytes. Increased activity of the enzymes superoxide dismutase, glutathione S-transferase and glucose 6-phosphate dehydrogenase was observed after exposure to PD. Furthermore, both drugs caused an increase in the activity of the enzymes catalase and glutathione peroxidase. However, only PD caused oxidative stress in exposed tadpoles, evidenced by increased levels of malondialdehyde and carbonyl proteins. Both drugs caused an increase in inflammatory infiltrates, blood cells and melanomacrophages in the liver. Our results indicate that PD was more toxic than PL, affecting development and causing oxidative stress.
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Affiliation(s)
- Camila Fatima Rutkoski
- Environmental Engineering Post-Graduation Program, University of Blumenau, Blumenau, SC, Brazil
| | - Suelen Cristina Grott
- Environmental Engineering Post-Graduation Program, University of Blumenau, Blumenau, SC, Brazil
| | - Nicole Grasmuk Israel
- Environmental Engineering Post-Graduation Program, University of Blumenau, Blumenau, SC, Brazil
| | | | | | - Daiane Bitschinski
- Biodiversity Post-Graduation Program, University of Blumenau, Blumenau, SC, Brazil
| | - Aline Warsneski
- Environmental Engineering Post-Graduation Program, University of Blumenau, Blumenau, SC, Brazil
| | - Priscila Aparecida Horn
- Environmental Engineering Post-Graduation Program, University of Blumenau, Blumenau, SC, Brazil
| | - Daína Lima
- Laboratory of Biomarkers of Aquatic Contamination and Immunochemistry, Department of Biochemistry, Federal University of Santa Catarina, UFSC, Florianópolis, SC, Brazil
| | - Camila Lisarb Velasquez Bastolla
- Laboratory of Biomarkers of Aquatic Contamination and Immunochemistry, Department of Biochemistry, Federal University of Santa Catarina, UFSC, Florianópolis, SC, Brazil
| | - Jacó Joaquim Mattos
- Laboratory of Biomarkers of Aquatic Contamination and Immunochemistry, Department of Biochemistry, Federal University of Santa Catarina, UFSC, Florianópolis, SC, Brazil
| | - Afonso Celso Dias Bainy
- Laboratory of Biomarkers of Aquatic Contamination and Immunochemistry, Department of Biochemistry, Federal University of Santa Catarina, UFSC, Florianópolis, SC, Brazil
| | | | | | - Thiago Caique Alves
- Environmental Engineering Post-Graduation Program, University of Blumenau, Blumenau, SC, Brazil
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da Silva PR, Borges-Martins M, Oliveira GT. Impacts of isolated or mixed Roundup® Original DI and Boral® 500 SC herbicides on the survival and metamorphosis of Melanophryniscus admirabilis tadpoles. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2023; 264:106715. [PMID: 37820410 DOI: 10.1016/j.aquatox.2023.106715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2023] [Revised: 09/29/2023] [Accepted: 10/01/2023] [Indexed: 10/13/2023]
Abstract
The bufonid species Melanophryniscus admirabilis is restricted to a single location in the southern Atlantic Forest, Brazil. Although the site of occurrence of M. admirabilis is covered with native forest and it is not directly exposed to pesticides application, the area is surrounded by agricultural activity. Our objectives were to evaluate possible alterations in morphological parameters (body mass, snout-vent length, and body index), metamorphosis (time to reach Gosner stages 42, 46 and to complete metamorphosis), and survival of M. admirabilis exposed to isolated Roundup® Original DI (R1: 234 and R2: 2340 µg.L-1 of glyphosate) and Boral® 500 SC, (B1: 130 and B2: 980 µg.L-1 of sulfentrazone) or mixed (R1+B1, R2+B1, R1+B2, R2+B2). Spawns of M. admirabilis were collected in natural lakes in the municipality of Arvorezinha and taken to laboratory cultivation. After the tadpoles acquired free swimming, the animals were acclimated for five days and fed ad libitum. The aquariums were contaminated with herbicides on the sixth day of cultivation, and the animals stayed in these aquariums for four days. Afterwards, the tadpoles were transferred to aquariums with clean water and monitored until metamorphosis (Gosner stage 46), when they were weighed, measured (snout-cloacal length) and cryoeuthanized. We observed no alterations in morphological parameters; however, survival was reduced in exposed groups (mortality index: 71 % in R2 and 29-64 % in mixed groups), suggesting energy allocation for metamorphosis at the expense of survival. Boral did not alter metamorphosis time. Roundup isolated and mixed with Boral altered the timing of Gosner stages 42 and 46 and reduced metamorphosis time, suggesting endocrine disruption. Thus, monitoring the presence and limiting the use of these pesticides in the area where M. admirabilis occurs can be crucial for conservation strategies.
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Affiliation(s)
- Patrícia Rodrigues da Silva
- Conservation Physiology Laboratory, Morphological Sciences Department, Postgraduate Program in Ecology and Evolution of Biodiversity, School of Health Sciences and Life, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Ipiranga ave. 6681 Building 12 C, Porto Alegre, Brazil
| | - Márcio Borges-Martins
- Herpetology Laboratory, Zoology Department, Postgraduate Program in Animal Biology, Biological Sciences Institute, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Guendalina Turcato Oliveira
- Conservation Physiology Laboratory, Morphological Sciences Department, Postgraduate Program in Ecology and Evolution of Biodiversity, School of Health Sciences and Life, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Ipiranga ave. 6681 Building 12 C, Porto Alegre, Brazil.
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3
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Ruthsatz K, Rico-Millan R, Eterovick PC, Gomez-Mestre I. Exploring water-borne corticosterone collection as a non-invasive tool in amphibian conservation physiology: benefits, limitations and future perspectives. CONSERVATION PHYSIOLOGY 2023; 11:coad070. [PMID: 37663928 PMCID: PMC10472495 DOI: 10.1093/conphys/coad070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 08/03/2023] [Accepted: 08/26/2023] [Indexed: 09/05/2023]
Abstract
Global change exposes wildlife to a variety of environmental stressors and is affecting biodiversity worldwide, with amphibian population declines being at the forefront of the global biodiversity crisis. The use of non-invasive methods to determine the physiological state in response to environmental stressors is therefore an important advance in the field of conservation physiology. The glucocorticoid hormone corticosterone (CORT) is one useful biomarker to assess physiological stress in amphibians, and sampling water-borne (WB) CORT is a novel, non-invasive collection technique. Here, we tested whether WB CORT can serve as a valid proxy of organismal levels of CORT in larvae of the common frog (Rana temporaria). We evaluated the association between tissue and WB CORT levels sampled from the same individuals across ontogenetic stages, ranging from newly hatched larvae to froglets at 10 days after metamorphosis. We also investigated how both tissue and WB CORT change throughout ontogeny. We found that WB CORT is a valid method in pro-metamorphic larvae as values for both methods were highly correlated. In contrast, there was no correlation between tissue and WB CORT in newly hatched, pre-metamorphic larvae, metamorphs or post-metamorphic froglets probably due to ontogenetic changes in respiratory and skin morphology and physiology affecting the transdermal CORT release. Both collection methods consistently revealed a non-linear pattern of ontogenetic change in CORT with a peak at metamorphic climax. Thus, our results indicate that WB CORT sampling is a promising, non-invasive conservation tool for studies on late-stage amphibian larvae. However, we suggest considering that different contexts might affect the reliability of WB CORT and consequently urge future studies to validate this method whenever it is used in new approaches. We conclude proposing some recommendations and perspectives on the use of WB CORT that will aid in broadening its application as a non-invasive tool in amphibian conservation physiology.
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Affiliation(s)
- Katharina Ruthsatz
- Zoological Institute, Technische Universität Braunschweig, Mendelssohnstraße 4, 38106 Braunschweig, Germany
| | - Rafael Rico-Millan
- Ecology, Evolution, and Development Group, Doñana Biological Station – CSIC, Calle Américo Vespucio 26, 41092 Seville, Spain
| | - Paula Cabral Eterovick
- Zoological Institute, Technische Universität Braunschweig, Mendelssohnstraße 4, 38106 Braunschweig, Germany
| | - Ivan Gomez-Mestre
- Ecology, Evolution, and Development Group, Doñana Biological Station – CSIC, Calle Américo Vespucio 26, 41092 Seville, Spain
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4
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Tornabene BJ, Crespi EJ, Breuner CW, Hossack BR. Testing whether adrenal steroids mediate phenotypic and physiologic effects of elevated salinity on larval tiger salamanders. Integr Zool 2023; 18:27-44. [PMID: 35848709 DOI: 10.1111/1749-4877.12669] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Salinity (sodium chloride, NaCl) from anthropogenic sources is a persistent contaminant that negatively affects freshwater taxa. Amphibians can be susceptible to salinity, but some species are innately or adaptively tolerant. Physiological mechanisms mediating tolerance to salinity are still unclear, but changes in osmoregulatory hormones such as corticosterone (CORT) and aldosterone (ALDO) are prime candidates. We exposed larval barred tiger salamanders (Ambystoma mavortium) to environmentally relevant NaCl treatments (<32-4000 mg·L-1 ) for 24 days to test effects on growth, survival, and waterborne CORT responses. Of those sampled, we also quantified waterborne ALDO from a subset. Using a glucocorticoid antagonist (RU486), we also experimentally suppressed CORT signaling of some larvae to determine if CORT mediates effects of salinity. There were no strong differences in survival among salinity treatments, but salinity reduced dry mass, snout-vent length, and body condition while increasing water content of larvae. High survival and sublethal effects demonstrated that salamanders were physiologically challenged but could tolerate the experimental concentrations. CORT signaling did not attenuate sublethal effects of salinity. Baseline and stress-induced (after an acute stressor, shaking) CORT were not influenced by salinity. ALDO was correlated with baseline CORT, suggesting it could be difficult to decouple the roles of CORT and ALDO. Future studies comparing ALDO and CORT responses of adaptively tolerant and previously unexposed populations could be beneficial to understand the roles of these hormones in tolerance to salinity. Nevertheless, our study enhances our understanding of the roles of corticosteroid hormones in mediating effects of a prominent anthropogenic stressor.
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Affiliation(s)
- Brian J Tornabene
- Wildlife Biology Program, W.A. Franke College of Forestry & Conservation, University of Montana, Missoula, Montana, USA
| | - Erica J Crespi
- School of Biological Sciences, Center for Reproductive Sciences, Washington State University, Pullman, Washington, USA
| | - Creagh W Breuner
- Wildlife Biology Program, W.A. Franke College of Forestry & Conservation, University of Montana, Missoula, Montana, USA
| | - Blake R Hossack
- Wildlife Biology Program, W.A. Franke College of Forestry & Conservation, University of Montana, Missoula, Montana, USA.,U.S. Geological Survey, Northern Rocky Mountain Science Center, Missoula, Montana, USA
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Paul B, Shewade LH, Buchholz DR. cyp21a2 Knockout Tadpoles Survive Metamorphosis Despite Low Corticosterone. Endocrinology 2022; 164:6775874. [PMID: 36301177 DOI: 10.1210/endocr/bqac182] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Indexed: 01/16/2023]
Abstract
Corticosteroids are so vital for organ maturation that reduced corticosteroid signaling during postembryonic development causes death in terrestrial vertebrates. Indeed, death occurs at metamorphosis in frogs lacking proopiomelanocortin (pomc) or the glucocorticoid receptor (GR; nr3c1). Some residual corticosteroids exist in pomc mutants to activate the wild-type (WT) GR and mineralocorticoid receptor (MR), and the elevated corticosteroids in GR mutants may activate MR. Thus, we expected a more severe developmental phenotype in tadpoles with inactivation of 21-hydroxylase, which should eliminate all interrenal corticosteroid biosynthesis. Using CRISPR/Cas9 in Xenopus tropicalis, we produced an 11-base pair deletion in cyp21a2, the gene encoding 21-hydroxylase. Growth and development were delayed in cyp21a2 mutant tadpoles, but unlike the other frog models, they survived metamorphosis. Consistent with an absence of 21-hydroxylase, mutant tadpoles had a 95% reduction of aldosterone in tail tissue, but they retained some corticosterone (∼40% of WT siblings), an amount, however, too low for survival in pomc mutants. Decreased corticosteroid signaling was evidenced by reduced expression of corticosteroid-response gene, klf9, and by impaired negative feedback in the hypothalamus-pituitary-interrenal axis with higher messenger RNA expression levels of crh, pomc, star, and cyp11b2 and an approximately 30-fold increase in tail content of progesterone. In vitro tail-tip culture showed that progesterone can transactivate the frog GR. The inadequate activation of GR by corticosterone in cyp21a2 mutants was likely compensated for by sufficient corticosteroid signaling from other GR ligands to allow survival through the developmental transition from aquatic to terrestrial life.
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Affiliation(s)
- Bidisha Paul
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221, USA
| | - Leena H Shewade
- Biotherapeutics Division, Codexis Inc., San Carlos, CA 94070, USA
| | - Daniel R Buchholz
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221, USA
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Regueira E, O'Donohoe MEA, Pavón Novarin M, Michou Etcheverría GC, Tropea C, Hermida GN. Integrating morphology and physiology of the key endocrine organ during tadpole development: The interrenal gland. J Anat 2022; 241:1357-1370. [PMID: 36056596 DOI: 10.1111/joa.13759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2022] [Revised: 08/09/2022] [Accepted: 08/17/2022] [Indexed: 11/26/2022] Open
Abstract
Indirect development is widespread in anurans and is considered an ancestral condition. The metamorphosis of larvae into juveniles involves highly coordinated morphological, physiological, biochemical, and behavioral changes, promoted by the thyroid hormone and interrenal corticosteroids. Stress response to environmental changes is also mediated by corticosteroids, affecting the timing and rate of metamorphosis and leading to great developmental plasticity in tadpoles. Given the potential effect of interrenal gland ontogeny alterations on metamorphosis and the lack of studies addressing both the morphology and endocrinology of this gland in tadpoles, we present corticosterone (CORT) production and histological changes through the ontogeny of interrenal gland in the generalized pond-type tadpole of Rhinella arenarum (Anura, Bufonidae). This species shows the highest concentration of whole-body CORT by the early climax when drastic metamorphic changes begin. This is coincident with the morphological differentiation of steroidogenic cells and the formation of interrenal cords. By this stage, steroidogenic cells have a shrunken cytoplasm, with a significantly higher nucleus-to-cell diameter ratio. The lowest CORT concentration during premetamorphosis and late climax is associated with small undifferentiated cells with lipid inclusions surrounding large blood vessels between kidneys, and with cords of differentiated steroidogenic cells with a significantly lower nucleus-to-cell diameter ratio, respectively. Our study characterizes the morphological and physiological pattern of interrenal gland development, showing an association between certain histological and morphometric characteristics and CORT levels. Variations in this morpho-physiological pattern should be considered when studying the phenotypic plasticity or variable growth rates of tadpoles.
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Affiliation(s)
- Eleonora Regueira
- Laboratorio Biología de Anfibios - Histología Animal, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, CABA, Argentina
| | - M E Ailín O'Donohoe
- Laboratorio Biología de Anfibios - Histología Animal, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA, Argentina.,Consejo Nacional de Investigaciones Científicas y Técnicas, CABA, Argentina
| | - Mariela Pavón Novarin
- Laboratorio Biología de Anfibios - Histología Animal, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA, Argentina
| | - Gabriela C Michou Etcheverría
- Laboratorio Biología de Anfibios - Histología Animal, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA, Argentina
| | - Carolina Tropea
- Consejo Nacional de Investigaciones Científicas y Técnicas, CABA, Argentina.,Laboratorio de Biología de la Reproducción y el Crecimiento de Crustáceos Decápodos, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires, CABA, Argentina
| | - Gladys N Hermida
- Laboratorio Biología de Anfibios - Histología Animal, Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, CABA, Argentina
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Reichert LMM, de Oliveira DR, Papaleo JL, Valgas AAN, Oliveira GT. Biochemical and body condition markers in Rhinella icterica tadpoles exposed to atrazine, glyphosate, and quinclorac based herbicides in ecologically relevant concentrations. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2022; 93:103884. [PMID: 35577267 DOI: 10.1016/j.etap.2022.103884] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 05/01/2022] [Accepted: 05/10/2022] [Indexed: 06/15/2023]
Abstract
Amphibians have suffered population decline due to several factors, including exposure to pesticides. In the south of Brazil, rice cultivations use herbicides based on atrazine, glyphosate and quinclorac as the commercial formulations Primoleo®, Roundup® and Facet®, respectively. Rhinella icterica was chosen to evaluate oxidative balance markers and body condition after exposure to three concentrations of herbicides (10, 20 and 40 µg/L of atrazine and quinclorac; 100, 250 and 500 µg/L of glyphosate). These xenobiotics, regardless of the concentrations used, accelerated the development process of animals and seemed to act as modulators of development. We observed no significant variations for any of the oxidative balance markers studied (superoxide dismutase, catalase, TBARS and carbonylated proteins); however, we cannot rule out that other antioxidant system components prevent oxidative stress. In general, atrazine and glyphosate accelerated the development of tadpoles, and quinclorac retards this process, which could impact the survival of these animals.
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Affiliation(s)
- Leici Maria Machado Reichert
- Pontifical Catholic University of Rio Grande do Sul, PUCRS, School of Health and Life Sciences, Conservation Physiology Laboratory, Brazil; PPG- Ecology and Biodiversity Evolution.
| | - Diogo Reis de Oliveira
- Pontifical Catholic University of Rio Grande do Sul, PUCRS, School of Health and Life Sciences, Conservation Physiology Laboratory, Brazil.
| | - Jonas Londero Papaleo
- Pontifical Catholic University of Rio Grande do Sul, PUCRS, School of Health and Life Sciences, Conservation Physiology Laboratory, Brazil.
| | - Artur Antunes Navarro Valgas
- Pontifical Catholic University of Rio Grande do Sul, PUCRS, School of Health and Life Sciences, Conservation Physiology Laboratory, Brazil; PPG, Animal Biology (Federal University of Rio Grande do Sul), Brazil.
| | - Guendalina Turcato Oliveira
- Pontifical Catholic University of Rio Grande do Sul, PUCRS, School of Health and Life Sciences, Conservation Physiology Laboratory, Brazil; PPG- Ecology and Biodiversity Evolution.
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8
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Tornabene BJ, Hossack BR, Crespi EJ, Breuner CW. Corticosterone mediates a growth-survival tradeoff for an amphibian exposed to increased salinity. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 335:703-715. [PMID: 34370904 DOI: 10.1002/jez.2535] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 06/24/2021] [Accepted: 07/26/2021] [Indexed: 01/01/2023]
Abstract
Life-history tradeoffs are common across taxa, but growth-survival tradeoffs-usually enhancing survival at a cost to growth-are less frequently investigated. Increased salinity (NaCl) is a prevalent anthropogenic disturbance that may cause a growth-survival tradeoff for larval amphibians. Although physiological mechanisms mediating tradeoffs are seldom investigated, hormones are prime candidates. Corticosterone (CORT) is a steroid hormone that independently influences survival and growth and may provide mechanistic insight into growth-survival tradeoffs. We conducted a 24-day experiment to test effects of salinity (<32-4000 mg/L) on growth, development, survival, CORT responses, and tradeoffs among traits of larval Northern Leopard Frogs (Rana pipiens). We also experimentally suppressed CORT signaling to determine whether CORT signaling mediates effects of salinity and a growth-survival tradeoff. Increased salinity reduced survival, growth, and development. Suppressing CORT signaling in conjunction with salinity reduced survival further but also attenuated the negative effects of salinity on growth, development, and water content. CORT of control larvae increased or was stable with growth and development but decreased with growth and development for those exposed to salinity. Therefore, salinity dysregulated CORT physiology. Across all treatments, larvae that survived had higher CORT than larvae that died. By manipulating CORT signaling, we provide strong evidence that CORT physiology mediates the outcome of a growth-survival tradeoff and enhances survival. To our knowledge, this is the first study to concomitantly measure tradeoffs between growth and survival and experimentally link these changes to CORT physiology. Identifying mechanistic links between stressors and fitness-related outcomes is critical to enhance our understanding of tradeoffs.
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Affiliation(s)
- Brian J Tornabene
- Wildlife Biology Program, W.A. Franke College of Forestry and Conservation, University of Montana, Missoula, Montana, USA
| | - Blake R Hossack
- Wildlife Biology Program, W.A. Franke College of Forestry and Conservation, University of Montana, Missoula, Montana, USA.,US Geological Survey, Northern Rocky Mountain Science Center, Missoula, Montana, USA
| | - Erica J Crespi
- School of Biological Sciences, Center for Reproductive Sciences, Washington State University, Pullman, Washington, USA
| | - Creagh W Breuner
- Wildlife Biology Program, W.A. Franke College of Forestry and Conservation, University of Montana, Missoula, Montana, USA
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9
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Tornabene BJ, Hossack BR, Crespi EJ, Breuner CW. Evaluating corticosterone as a biomarker for amphibians exposed to increased salinity and ambient corticosterone. CONSERVATION PHYSIOLOGY 2021; 9:coab049. [PMID: 34249364 PMCID: PMC8254138 DOI: 10.1093/conphys/coab049] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 05/28/2021] [Accepted: 06/10/2021] [Indexed: 06/13/2023]
Abstract
Physiological biomarkers are commonly used to assess the health of taxa exposed to natural and anthropogenic stressors. Glucocorticoid (GC) hormones are often used as indicators of physiological stress in wildlife because they affect growth, reproduction and survival. Increased salinity from human activities negatively influences amphibians and their corticosterone (CORT; the main amphibian GC) physiology; therefore, CORT could be a useful biomarker. We evaluated whether waterborne CORT could serve as a biomarker of salt stress for three free-living amphibian species that vary in their sensitivity to salinity: boreal chorus frogs (Pseudacris maculata), northern leopard frogs (Rana pipiens) and barred tiger salamanders (Ambystoma mavortium). Across a gradient of contamination from energy-related saline wastewaters, we tested the effects of salinity on baseline and stress-induced waterborne CORT of larvae. Stress-induced, but not baseline, CORT of leopard frogs increased with increasing salinity. Salinity was not associated with baseline or stress-induced CORT of chorus frogs or tiger salamanders. Associations between CORT and salinity were also not related to species-specific sensitivities to salinity. However, we detected background environmental CORT (ambient CORT) in all wetlands and spatial variation was high within and among wetlands. Higher ambient CORT was associated with lower waterborne CORT of larvae in wetlands. Therefore, ambient CORT likely confounded associations between waterborne CORT and salinity in our analysis and possibly influenced physiology of larvae. We hypothesize that larvae may passively take up CORT from their environment and downregulate endogenous CORT. Although effects of some hormones (e.g. oestrogen) and endocrine disruptors on aquatic organisms are well described, studies investigating the occurrence and effects of ambient CORT are limited. We provide suggestions to improve collection methods, reduce variability and avoid confounding effects of ambient CORT. By making changes to methodology, waterborne CORT could still be a promising, non-invasive conservation tool to evaluate effects of salinity on amphibians.
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Affiliation(s)
- Brian J Tornabene
- Wildlife Biology Program, W.A. Franke College of Forestry & Conservation, University of Montana, Missoula, MT 59812, USA
| | - Blake R Hossack
- Wildlife Biology Program, W.A. Franke College of Forestry & Conservation, University of Montana, Missoula, MT 59812, USA
- US Geological Survey, Northern Rocky Mountain Science Center, Missoula, MT 59812, USA
| | - Erica J Crespi
- School of Biological Sciences, Center for Reproductive Sciences, Washington State University, Pullman, WA 99163, USA
| | - Creagh W Breuner
- Wildlife Biology Program, W.A. Franke College of Forestry & Conservation, University of Montana, Missoula, MT 59812, USA
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10
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Titon SCM, Titon Junior B, Assis VR, Vasconcelos-Teixeira R, Garcia Neto PG, Lima AS, Ferreira LDF, Fernandes PA, Gomes FR, Markus RP. Hormonal daily variation co-varies with immunity in captive male bullfrogs (Lithobates catesbeianus). Gen Comp Endocrinol 2021; 303:113702. [PMID: 33359060 DOI: 10.1016/j.ygcen.2020.113702] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Revised: 08/12/2020] [Accepted: 12/13/2020] [Indexed: 11/25/2022]
Abstract
Almost all physiological processes within the organism, including immune parameters and hormones, follow a circadian rhythm. These daily fluctuations are often observed in free-living organisms; however, little is known regarding hormonal and immune daily variations in anurans, particularly under laboratory conditions. This study aimed to investigate the hormonal and immune daily variation in captive-bred Bullfrogs (Lithobates catesbeianus) under constant conditions (21 °C and 12:12 LD cycle). Our results showed a daily variation for plasma corticosterone (CORT), testosterone (T), and melatonin (MEL), as well as for blood leukocyte profile, phagocytic activity, and plasma bacterial killing ability (BKA). Hormonal profile and immune activity were higher at the dark when compared with the light phase; however, monocytes and lymphocytes followed the opposite pattern. Moreover, CORT was positively correlated with phagocytosis percentage of blood cells, BKA, and monocytes, while MEL and T showed a positive correlation with PP. Our results demonstrate the daily covariation of different immune variables and immunomodulatory hormones. These 24 h-day variations and covariation certainly have broad implications and need to be considered for better understanding anuran physiology both in the context of laboratory and field studies.
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Affiliation(s)
| | - Braz Titon Junior
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Vania Regina Assis
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | | | | | - Alan Siqueira Lima
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Letícia de França Ferreira
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Pedro A Fernandes
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Fernando Ribeiro Gomes
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
| | - Regina P Markus
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil
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11
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Hopkins WA, DuRant SE, Beck ML, Ray WK, Helm RF, Romero LM. Cortisol is the predominant glucocorticoid in the giant paedomorphic hellbender salamander (Cryptobranchus alleganiensis). Gen Comp Endocrinol 2020; 285:113267. [PMID: 31491375 DOI: 10.1016/j.ygcen.2019.113267] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Revised: 08/19/2019] [Accepted: 09/01/2019] [Indexed: 11/20/2022]
Abstract
Corticosterone is widely regarded to be the predominant glucocorticoid produced in amphibians. However, we recently described unusually low baseline and stress-induced corticosterone profiles in eastern hellbenders (Cryptobranchus alleganiensis alleganiensis), a giant, fully aquatic salamander. Here, we hypothesized that hellbenders might also produce cortisol, the predominant glucocorticoid used by fishes and non-rodent mammals. To test our hypothesis, we collected plasma samples in two field experiments and analyzed them using multiple analytical techniques to determine how plasma concentrations of cortisol and corticosterone co-varied after 1) physical restraint and 2) injection with adrenocorticotropic hormone (ACTH), the pituitary hormone responsible for triggering the release of glucocorticoids from amphibian interrenal glands. Using liquid chromatography-mass spectrometry, we found that baseline and restraint-induced plasma concentrations of cortisol were more than five times those of corticosterone. We then demonstrated that plasma concentrations of both glucocorticoids increased in response to ACTH in a dose-dependent manner, but cortisol concentrations were consistently higher (up to 10-fold) than corticosterone. Cortisol and corticosterone concentrations were not correlated with one another at basal or induced conditions. The extremely low plasma concentrations of corticosterone in hellbenders suggests that corticosterone could simply be a byproduct of cortisol production, and raises questions as to whether corticosterone has any distinct physiological function in hellbenders. Our results indicate that hellbenders produce cortisol as their predominant glucocorticoid, supporting a small and inconclusive body of literature indicating that some other amphibians may produce appreciable quantities of cortisol. We hypothesize that the use of cortisol by hellbenders could be an adaptation to their fully aquatic life history due to cortisol's ability to fulfill both mineralocorticoid and glucocorticoid functions, similar to its functions in fishes. Given the large number of amphibian species that are fully aquatic or have aquatic life stages, we suggest that the broadly held assumption that corticosterone is the predominant glucocorticoid in all amphibians requires further scrutiny. Ultimately, multi-species tests of this assumption will reveal the ecological factors that influenced the evolution of endocrine adaptations among amphibian lineages, and may provide insight into convergent evolution of endocrine traits in paedomorphic species.
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Affiliation(s)
- William A Hopkins
- Dept of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA 24061, USA.
| | - Sarah E DuRant
- Dept of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA
| | - Michelle L Beck
- Dept of Fish and Wildlife Conservation, Virginia Tech, Blacksburg, VA 24061, USA; Dept. of Biology, Rivier University, Nashua, NH 03060, USA
| | - W Keith Ray
- Dept of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA
| | - Richard F Helm
- Dept of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA
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12
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Wilkens ALL, Valgas AAN, Oliveira GT. Effects of ecologically relevant concentrations of Boral® 500 SC, Glifosato® Biocarb, and a blend of both herbicides on markers of metabolism, stress, and nutritional condition factors in bullfrog tadpoles. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2019; 26:23242-23256. [PMID: 31190300 DOI: 10.1007/s11356-019-05533-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 05/21/2019] [Indexed: 06/09/2023]
Abstract
The aim of this study was to verify the effects of the isolated forms of Boral® SC 500, Glifosato® Biocarb herbicides, and a blend of both herbicides on metabolism and oxidative balance markers of Rana catesbeiana tadpoles and on their nutritional condition. Groups of tadpoles were divided into different treatments: control (no herbicides), Boral® 500 SC (sulfentrazone: 130 μg/L), Glifosato® Biocarb (glyphosate: 234 μg/L), and a blend of both herbicides. After 7 days, the liver, caudal muscle, and blood samples were taken to subsequently perform the biomarkers determination by spectrophotometry. The intestinal condition factor increased in animals exposed to glyphosate and herbicide blends, suggesting a hyperphagic effect. This hypothesis was confirmed by the rise of triglycerides and circulating very low-density lipoprotein (VLDL). There was a significant increase in the levels of uric acid in tadpoles exposed to the herbicide blend. Corticosterone levels reduced significantly in animals exposed to glyphosate and the herbicide blend. Oxidative stress markers had a tissue-dependent response. In the liver, glutathione S-transferase increased, and superoxide dismutase and catalase decreased in animals exposed to sulfentrazone and glyphosate. Lipoperoxidation was reduced in the glyphosate treatment. In the caudal muscle, superoxide dismutase and catalase activities were maintained, and there was a decline in the levels of glutathione S-transferase and TBARS only in the blend group.
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Affiliation(s)
- Anike L L Wilkens
- School of Sciences, Conservation Physiology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil
- PPG-Ecology and Evolution of Biodiversity, Porto Alegre, Brazil
| | - Artur A N Valgas
- School of Sciences, Conservation Physiology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil
| | - Guendalina T Oliveira
- School of Sciences, Conservation Physiology Laboratory, Pontifícia Universidade Católica do Rio Grande do Sul, Porto Alegre, Brazil.
- PPG-Ecology and Evolution of Biodiversity, Porto Alegre, Brazil.
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13
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Gavel MJ, Richardson SD, Dalton RL, Soos C, Ashby B, McPhee L, Forbes MR, Robinson SA. Effects of 2 Neonicotinoid Insecticides on Blood Cell Profiles and Corticosterone Concentrations of Wood Frogs (Lithobates sylvaticus). ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2019; 38:1273-1284. [PMID: 30901102 DOI: 10.1002/etc.4418] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Revised: 01/19/2019] [Accepted: 03/14/2019] [Indexed: 06/09/2023]
Abstract
Neonicotinoids are widely used insecticides that are detectable in agricultural waterways. These insecticides are of concern due to their potential impacts on nontarget organisms. Pesticides can affect development of amphibians and suppress the immune system, which could impact disease susceptibility and tolerance. No previous studies on amphibians have examined the effects of these insecticides on differential blood cell proportions or concentrations of corticosterone (a general stress hormone). We investigated the effects of chronic exposure to 2 neonicotinoids, thiamethoxam and clothianidin, on immunometrics of wood frogs (Lithobates sylvaticus). Frogs were exposed to single, chronic treatments of 2.5 or 250 µg/L of clothianidin or thiamethoxam for 7 wk from Gosner stages 25 to 46. The juvenile frogs were then maintained for 3 wk post metamorphosis without exposure to neonicotinoids. We measured water-borne corticosterone twice: at 6 d and 8 wk after exposure in larval and juvenile frogs, respectively. We assessed differential blood cell profiles from juvenile frogs. Corticosterone was significantly lower in tadpoles exposed to 250 µg/L of thiamethoxam compared with other tadpole treatments, but no significant differences in corticosterone concentrations were found in treatments using juvenile frogs. Anemia was detected in all treatments compared with controls with the exception of tadpoles exposed to 2.5 µg/L of clothianidin. Neutrophil-to-leukocyte and neutrophil-to-lymphocyte ratios were elevated in frogs exposed to 250 µg/L of thiamethoxam. Collectively, these results indicate that chronic exposure to neonicotinoids has varied impacts on blood cell profiles and corticosterone concentrations of developing wood frogs, which are indicative of stress. Future studies should investigate whether exposure to neonicotinoids increases susceptibility to infection by parasites in both larval and adult wood frogs. Environ Toxicol Chem 2019;38:1273-1284. © 2019 Crown in the right of Canada. Published by Wiley Periodicals Inc. on behalf of SETAC.
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Affiliation(s)
- Melody J Gavel
- Department of Biology, Carleton University, Ottawa, Ontario, Canada
| | | | - Rebecca L Dalton
- Department of Biology, Carleton University, Ottawa, Ontario, Canada
- Science and Technology Branch, Science and Risk Assessment Directorate, Ecological Assessment Division, Environment and Climate Change Canada, Gatineau, Quebec, Canada
| | - Catherine Soos
- Science and Technology Branch, Wildlife and Landscape Science Directorate, Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Saskatoon, Saskatchewan, Canada
- Department of Veterinary Pathology, University of Saskatchewan, Saskatoon, Canada
| | - Brendan Ashby
- Science and Technology Branch, Wildlife and Landscape Science Directorate, Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Saskatoon, Saskatchewan, Canada
| | - Landon McPhee
- Science and Technology Branch, Wildlife and Landscape Science Directorate, Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Saskatoon, Saskatchewan, Canada
| | - Mark R Forbes
- Department of Biology, Carleton University, Ottawa, Ontario, Canada
| | - Stacey A Robinson
- Science and Technology Branch, Wildlife and Landscape Science Directorate, Ecotoxicology and Wildlife Health Division, Environment and Climate Change Canada, Ottawa, Ontario, Canada
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14
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Massé AJ, Muscatello JR, Hogan NS, Janz DM. Tissue-specific selenium accumulation and toxicity in adult female Xenopus laevis chronically exposed to elevated dietary selenomethionine. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2017; 36:1047-1055. [PMID: 27666932 DOI: 10.1002/etc.3627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 05/10/2016] [Accepted: 09/22/2016] [Indexed: 06/06/2023]
Abstract
Selenium (Se) is a developmental toxicant that is also capable of altering the bioenergetic and endocrine status of adult fish. To date, aquatic ecotoxicological research has predominantly focused on the toxic effects of Se in fish, and minimal information has been published related to amphibians. The objective of the present study was to investigate the potential toxicity associated with chronically elevated dietary Se consumption in adult female amphibians utilizing the model species Xenopus laevis. Adult X. laevis females were fed a diet augmented with L-selenomethionine at measured concentrations of 0.7 µg Se/g (control), 10.9 µg Se/g, 30.4 µg Se/g, or 94.2 µg Se/g dry mass for 68 d, after which they were bred with untreated males. Ovary, egg, liver, muscle, and blood samples were collected from female frogs after completion of the exposure period and subsequent breeding to ascertain Se tissue distribution, muscle and liver triglyceride and glycogen levels, and plasma cortisol concentrations. The concentrations of Se measured in female tissues excluding the liver were significantly increased in proportion with dietary intake. No significant differences were observed among treatment groups with respect to biometric indices, energy stores, or stress response of adult female X. laevis after Se exposure, which suggests that this amphibian species is capable of accumulating substantial quantities of this element in their tissues with no adverse effects on fitness. Environ Toxicol Chem 2017;36:1047-1055. © 2016 SETAC.
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Affiliation(s)
- Anita J Massé
- Toxicology Graduate Program, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | | | - Natacha S Hogan
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - David M Janz
- Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
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15
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Falso PG, Noble CA, Diaz JM, Hayes TB. The effect of long-term corticosterone treatment on blood cell differentials and function in laboratory and wild-caught amphibian models. Gen Comp Endocrinol 2015; 212:73-83. [PMID: 25616196 DOI: 10.1016/j.ygcen.2015.01.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2014] [Revised: 01/10/2015] [Accepted: 01/13/2015] [Indexed: 02/05/2023]
Abstract
The effect of long-term stress on amphibian immunity is not well understood. We modeled a long-term endocrine stress scenario by elevating plasma corticosterone in two species of amphibians and examined effects on white blood cell differentials and innate immune activity. Plasma corticosterone was elevated in American bullfrogs (Lithobates catesbeianus) by surgically implanting corticosterone capsules and in African clawed frogs (Xenopus laevis) by immersion in corticosterone-treated water. To provide a context for our results within endogenous corticosterone fluctuations, diurnal plasma corticosterone cycles were determined. A daily low of corticosterone was observed in X. laevis at 12:00, while a significant pattern was not observed in L. catesbeianus. Elevated plasma corticosterone levels increased the ratio of peripheral neutrophils to lymphocytes, in both species, and decreased eosinophil concentrations in L. catesbeianus over a long-term period. Whole blood oxidative burst generally correlated with neutrophil concentrations, and thus was increased with corticosterone treatment, significantly in L. catesbeianus. In L. catesbeianus, an endogenous response of eosinophils and lymphocytes to implanted empty (sham) capsules was observed, but this effect was attenuated by corticosterone. Peripheral monocyte and basophil concentrations were not significantly altered by corticosterone treatment in either species. Our results show that long-term stress can alter amphibian immune parameters for extended periods and may play a role in susceptibility to disease.
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Affiliation(s)
- Paul G Falso
- Department of Biology, Slippery Rock University, Slippery Rock, PA 16057, USA.
| | - Christopher A Noble
- Laboratory for Integrative Studies in Amphibian Biology, Molecular Toxicology Group, and Integrative Biology Department, University of California, Berkeley, CA 94720-3140, USA.
| | - Jesus M Diaz
- Laboratory for Integrative Studies in Amphibian Biology, Molecular Toxicology Group, and Integrative Biology Department, University of California, Berkeley, CA 94720-3140, USA.
| | - Tyrone B Hayes
- Laboratory for Integrative Studies in Amphibian Biology, Molecular Toxicology Group, and Integrative Biology Department, University of California, Berkeley, CA 94720-3140, USA.
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16
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Kulkarni SS, Buchholz DR. Corticosteroid signaling in frog metamorphosis. Gen Comp Endocrinol 2014; 203:225-31. [PMID: 24713447 DOI: 10.1016/j.ygcen.2014.03.036] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Revised: 03/20/2014] [Accepted: 03/22/2014] [Indexed: 10/25/2022]
Abstract
Stress in fetal and larval life can impact later health and fitness in humans and wildlife. Long-term effects of early life stress are mediated by altered stress physiology induced during the process of relaying environmental effects on development. Amphibian metamorphosis has been an important model system to study the role of hormones in development in an environmental context. Thyroid hormone (TH) is necessary and sufficient to initiate the dramatic morphological and physiological changes of metamorphosis, but TH alone is insufficient to complete metamorphosis. Other hormones, importantly corticosteroid hormones (CSs), influence the timing and nature of post-embryonic development. Stressors or treatments with CSs delay or accelerate metamorphic change, depending on the developmental stage of treatment. Also, TH and CSs have synergistic, antagonistic, and independent effects on gene regulation. Importantly, the identity of the endogenous corticosteroid hormone or receptor underlying any gene induction or remodeling event has not been determined. Levels of both CSs, corticosterone and aldosterone, peak at metamorphic climax, and the corticosteroid receptors, glucocorticoid and mineralocorticoid receptors, have wide expression distribution among tadpole tissues. Conclusive experiments to identify the endogenous players have been elusive due to difficulties in experimental control of corticosteroid production and signaling. Current data are consistent with the hypothesis that the two CSs and their receptors serve largely overlapping functions in regulating metamorphosis and synergy with TH. Knowledge of the endogenous players is critical to understanding the basic mechanisms and significance of corticosteroid action in regulating post-embryonic development in environmental contexts.
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Affiliation(s)
- Saurabh S Kulkarni
- Department of Pediatrics, Yale University School of Medicine, New Haven, CT 06520, United States
| | - Daniel R Buchholz
- Department of Biological Sciences, University of Cincinnati, Cincinnati, OH 45221, United States.
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17
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Uchiyama M, Maejima S, Wong MKS, Preyavichyapugdee N, Wanichanon C, Hyodo S, Takei Y, Matuda K. Changes in plasma angiotensin II, aldosterone, arginine vasotocin, corticosterone, and electrolyte concentrations during acclimation to dry condition and seawater in the crab-eating frog. Gen Comp Endocrinol 2014; 195:40-6. [PMID: 24184110 DOI: 10.1016/j.ygcen.2013.10.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Revised: 10/15/2013] [Accepted: 10/17/2013] [Indexed: 10/26/2022]
Abstract
The crab-eating frog Fejervarya cancrivora inhabits mangrove swamps and marshes in Southeast Asia. In the present study, circulating angiotensin II (Ang II), aldosterone (Aldo), arginine vasotocin (AVT), and corticosterone (Cort) concentrations as well as various blood parameters were studied under osmotically stressful conditions. Following acclimation to hyperosmotic seawater and dry condition for 5days, body weight was significantly decreased. Under both conditions, plasma Na(+), Cl(-), and urea concentrations, hematocrit values (Ht; blood volume indicator), and osmolality were significantly increased. Dehydration associated with hypovolemic and hyperosmotic states of body fluids was induced during acclimation to hyperosmotic seawater and dry condition in the crab-eating frogs. Ang II, Aldo, AVT, and Cort were maintained within relatively narrow concentration ranges in the control frogs; however, in frogs under dry and hyperosmotic seawater conditions, large variations were observed among individuals in each group. Mean plasma Ang II and Aldo concentrations significantly increased in hyperosmotic seawater-acclimated and desiccated frogs. Although mean plasma AVT concentrations in dehydrated frogs of both the groups were approximately 2.0-3.5 times higher than those in the control frogs, the differences were not significant because of the variation. There was a significant correlation between plasma osmolality and AVT as well as Ang II but not Aldo. A significant correlation was also observed between Ht and AVT as well as Ang II. Plasma Ang II was significantly correlated with plasma Aldo. These results indicate that the crab-eating frogs may exhibit similar physiological responses to both seawater-acclimated and dry conditions. It appears that under dehydrated conditions, osmoregulatory mechanisms participate in stabilization of the situation. The renin-angiotensin system may have pivotal roles in body fluid regulation under volemic and osmotic stress in the Fejervarya species with unique osmoregulation.
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Affiliation(s)
- Minoru Uchiyama
- Department of Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan.
| | - Sho Maejima
- Department of Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan
| | - Marty K S Wong
- Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-15 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Narin Preyavichyapugdee
- Faculty of Animal Sciences and Agricultural Technology, Silpakorn University, Petchaburi IT Campus, Petchaburi 76120, Thailand
| | - Chaitip Wanichanon
- Department of Anatomy, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand
| | - Susumu Hyodo
- Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-15 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Yoshio Takei
- Department of Marine Biosciences, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-15 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | - Kouhei Matuda
- Department of Life and Environmental Science, Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan
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18
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Chambers DL, Wojdak JM, Du P, Belden LK. Pond acidification may explain differences in corticosterone among salamander populations. Physiol Biochem Zool 2013; 86:224-32. [PMID: 23434782 DOI: 10.1086/669917] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Physiological tolerances play a key role in determining species distributions and abundance across a landscape, and understanding these tolerances can therefore be useful in predicting future changes in species distributions that might occur. Vertebrates possess several highly conserved physiological mechanisms for coping with environmental stressors, including the hormonal stress response that involves an endocrine cascade resulting in the increased production of glucocorticoids. We examined the function of this endocrine axis by assessing both baseline and acute stress-induced concentrations of corticosterone in larvae from eight natural breeding populations of Jefferson's salamander Ambystoma jeffersonianum. We surveyed individuals from each pond and also examined a variety of environmental pond parameters. We found that baseline and stress-induced corticosterone concentrations differed significantly among ponds. Population-level baseline corticosterone concentrations were negatively related to pH and positively related to nitrate, and stress-induced concentrations were again negatively related to pH, positively related to nitrate, and positively related to temperature. We followed the field survey with an outdoor mesocosm experiment in which we manipulated pH and again examined baseline and acute stress-induced corticosterone in A. jeffersonianum larvae. As in the field survey, we observed an increase in the baseline corticosterone concentration of individuals exposed to the lowest pH treatment (pH 5-5.8). Examining physiological indices using a combined approach of field surveys and experiments can be a powerful tool for trying to unravel the complexities of environmental impacts on species distributions.
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Affiliation(s)
- David L Chambers
- Department of Biological Sciences, , Virginia Tech, Blacksburg, VA 24061, USA
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19
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Teixeira PC, Dias DC, Rocha GC, Antonucci AM, França FM, Marcantonio AS, Ranzani-Paiva MJT, Ferreira CM. Profile of cortisol, glycaemia, and blood parameters of American Bullfrog tadpoles Lithobates catesbeianus exposed to density and hypoxia stressors. PESQUISA VETERINARIA BRASILEIRA 2012. [DOI: 10.1590/s0100-736x2012001300016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The aim of this study was to evaluate alterations to the physiological profile (cortisol, glycaemia, and blood parameters) of Lithobates catesbeianus caused by the stressors density and hypoxia. The organisms were in the prometamorphosis stage and exposed to different tadpole densities: 1 tadpole/L (T1), 5 tadpoles/L (T2), and 10 tadpoles/L (T3) for 12 days. The blood was collected through the rupture of the caudal blood vessel and collected under normoxia (immediate collection) and hypoxia (after 15 minutes of air exposure) conditions. Cortisol levels rose on the fourth and eighth days of treatment and returned to basal levels by the end of the experiment. The stressor mechanisms tested did not affect glycaemia. White blood cells (total number of lymphocytes, neutrophils, and eosinophils) showed a significant difference at the twelfth day of the experiment when compared with the start of the experiment. We concluded that, under controlled conditions, a density of up to 10 tadpoles/L and air exposure for 15 minutes did not cause harmful physiological alterations during the experimental period. The answer to these stressors maybe was in another hormonal level (corticosterone).
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20
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Hernández SE, Sernia C, Bradley AJ. The effect of three anaesthetic protocols on the stress response in cane toads (Rhinella marina). Vet Anaesth Analg 2012; 39:584-90. [DOI: 10.1111/j.1467-2995.2012.00753.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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21
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Chambers DL, Wojdak JM, Du P, Belden LK. Corticosterone Level Changes throughout Larval Development in the Amphibians Rana sylvatica and Ambystoma jeffersonianum Reared under Laboratory, Mesocosm, or Free-living Conditions. COPEIA 2011. [DOI: 10.1643/cp-09-180] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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22
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Goymann W, Trappschuh M. Seasonal and diel variation of hormone metabolites in European stonechats: on the importance of high signal-to-noise ratios in noninvasive hormone studies. J Biol Rhythms 2011; 26:44-54. [PMID: 21252365 DOI: 10.1177/0748730410388394] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Most vertebrates living in seasonal environments show seasonal reproductive cycles and diel rhythms. The rhythmicity in behavior and morphology is accompanied by diel and seasonal patterns of hormone secretions. In small animals, the investigation of diel patterns of hormones has been hampered because repeated blood sampling is difficult and may influence subsequent measurements. A possibility to avoid these caveats is to investigate excreted hormone metabolites instead. Here, we describe the diel excretion patterns of testosterone and corticosterone metabolites in a small captive songbird during 4 seasons: winter, early spring (Zugunruhe), summer, and autumn molt. Our approach is quite unique, because the diel patterns of steroids have rarely--if at all--been investigated in the same individuals within several seasons. Small birds should be ideal to investigate diel patterns of hormone metabolites, because they defecate frequently enough to establish a diel profile. However, concentration measurements of hormone metabolites rely on the assumptions that hormone metabolites are placed into droppings of similar mass (the "dropping amount assumption") and are excreted in constant time intervals (the "constant interval assumption"). These assumptions were clearly violated in our study, as the dropping mass per time interval and the defecation intervals varied depending on the time of day and season. We thus used the rate of hormone metabolite excretion as an alternative measure to concentration. Both testosterone and corticosterone metabolites showed diel and seasonal rhythmicity. Furthermore, the diel pattern varied depending on season. Concentration and rate measurements gave similar results when the differences between hormone metabolite levels were large-for example, when testosterone metabolites were compared across seasons. When the differences were more subtle, though, the 2 measures did not always correspond well, indicating that the violation of the 2 basic assumptions affected the comparability of concentration measurements. We conclude that diel and seasonal comparisons of hormone metabolites potentially give biologically meaningful results, especially when rates instead of concentrations are measured. However, such studies require awareness of the limitations and pitfalls of noninvasive hormone measurements, a carefully designed experiment, and very cautious interpretation of the data.
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Affiliation(s)
- Wolfgang Goymann
- Max-Planck-Institut für Ornithologie, Abteilung für Verhaltensneurobiologie, Eberhard-Gwinner-Straße, Seewiesen, Germany.
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23
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Gay F, Valiante S, Sciarrillo R, De Falco M, Laforgia V, Capaldo A. Annual and daily serum aldosterone and catecholamine patterns in males of the Italian crested newt,Triturus carnifex(Amphibia, Urodela). ACTA ACUST UNITED AC 2010. [DOI: 10.1080/11250000903334302] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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24
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Rocha GC, Ferreira CM, Teixeira PC, Dias DC, França FM, Antonucci AM, Marcantonio AS, Lauretto M. Physiological response of American bullfrog tadpoles to stressor conditions of capture and hypoxia. PESQUISA VETERINÁRIA BRASILEIRA 2010. [DOI: 10.1590/s0100-736x2010001000014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The American bullfrog (Rana catesbeiana), recently named Lithobates catesbeianus is currently farmed for commercial purposes throughout various regions of Brazil. Stressful situations such as problems of management, inadequate facilities and environmental changes with consequent reduction of immunity are common in intensive production. The assessments of these situations of stress allow us detect these problems decreasing the injuries causes by confinement. The main objective of this study was to use the biological markers of plasma cortisol and glucose level and hematological parameters to evaluate the response of bullfrog tadpoles submitted to stressed mechanisms of capture and hypoxia. The animals were subjected to three treatments: stress due to individual capture with a hand net; stress due to batch capture with a hand net; and stress due to capture by emptying. The results obtained demonstrated that there were no statistically significant differences in the parameters tested when comparing the treatments with and without exposure to air (normoxia and hypoxia). Based on these results we can conclude that the stressful stimuli tested were not adequate to alter the biomarker tested. For the cortisol, probably this should have occurred due to the synergistic action between this hormone and thyroxin, which induces metamorphosis in these animals.
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Sundqvist M. Developmental changes of purinergic control of intestinal motor activity during metamorphosis in the African clawed frog, Xenopus laevis. Am J Physiol Regul Integr Comp Physiol 2007; 292:R1916-25. [PMID: 17272661 DOI: 10.1152/ajpregu.00785.2006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Little is known about the purinergic regulation of intestinal motor activity in amphibians. Purinergic control of intestinal motility is subject to changes during development in mammals. The aim of this study was to investigate purinergic control of intestinal smooth muscle in the amphibian Xenopus laevis and explore possible changes in this system during the developmental phase of metamorphosis. Effects of purinergic compounds on mean force and contraction frequency in intestinal circular muscle strips from prometamorphic, metamorphic, and juvenile animals were investigated. Before metamorphosis, low concentrations of ATP reduced motor activity, whereas the effects were reversed at higher concentrations. ATP-induced relaxation was not inhibited by the P2-receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) but was blocked by the ecto-nucleotidase inhibitor 6-N,N-diethyl-d-beta,gamma-dibromomethylene ATP (ARL67256), indicating that an ATP-derived metabolite mediated the relaxation response at this stage. Adenosine induced relaxation before, during, and after metamorphosis, which was blocked by the A(1)-receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX). The stable ATP-analog adenosine 5'-[gamma-thio]-triphosphate (ATPgammaS) and 2-methylthioATP (2-MeSATP) elicited contractions in the circular muscle strips in prometamorphic tadpoles. However, in juvenile froglets, 2-MeSATP caused relaxation, as did ATPgammaS at low concentrations. The P2Y(11)/P2X(1)-receptor antagonist NF157 antagonized the ATPgammaS-induced relaxation. The P2X-preferring agonist alpha-beta-methyleneadenosine 5'-triphosphate (alpha-beta-MeATP) evoked PPADS-sensitive increases in mean force at all stages investigated. This study demonstrates the existence of an adenosine A(1)-like receptor mediating relaxation and a P2X-like receptor mediating contraction in the X. laevis gut before, during, and after metamorphosis. Furthermore, the development of a P2Y(11)-like receptor-mediated relaxation during metamorphosis is shown.
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Wright ML, Francisco LL, Scott JL, Richardson SE, Carr JA, King AB, Noyes AG, Visconti RF. Effects of bilateral and unilateral ophthalmectomy on plasma melatonin in Rana tadpoles and froglets under various experimental conditions. Gen Comp Endocrinol 2006; 147:158-66. [PMID: 16458309 DOI: 10.1016/j.ygcen.2005.12.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2005] [Revised: 12/11/2005] [Accepted: 12/16/2005] [Indexed: 10/25/2022]
Abstract
The effect of ophthalmectomy (enucleation) on plasma melatonin in Rana tadpoles and froglets was studied under various experimental conditions to determine if ocular melatonin is released into the circulation from the eyes and to study the factors which might affect this process. Where operations occurred in early or mid-photophase on a 12 light:12 dark (12L:12D) cycle (light onset at 08:00 h), sampling in mid-light and mid-dark revealed that scotophase plasma melatonin was reduced at all developmental stages, with the more significant effects occurring before metamorphic climax. Experiments sampling prometamorphic tadpoles six times in a 24h period on 18L:6D, 12L:12D, or 6L:18D five days after enucleation also showed a significant lowering of plasma melatonin in the dark, so that the scotophase peak was virtually eliminated on all the LD cycles. These findings indicated that the reduction in plasma melatonin after bilateral eye removal was independent of the LD cycle and the metamorphic stage, and that it abolished the diel melatonin rhythm at the expense of the scotophase peak. Experiments carried out for 5 weeks suggested that compensatory secretion of melatonin by other organs after eye removal might partially restore the plasma melatonin level over time. Unilateral ophthalmectomy tended to reduce, but not eliminate, the night peak of plasma melatonin, and did not result in a compensatory increase in ocular melatonin in the remaining eye. Ophthalmectomized tadpoles exhibited darkening of the skin after the operation, which was not associated with a significant change in pituitary alpha-melanotropin. The findings overall indicate that the eyes in Rana tadpoles and froglets contribute up to somewhat over one-half of the circulating melatonin, particularly during the scotophase, and provide experimental evidence for ocular secretion into the blood for the first time in the Amphibia.
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Affiliation(s)
- Mary L Wright
- Department of Biology, College of Our Lady of the Elms, Chicopee, MA 01013, USA.
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Vafopoulou X, Steel CGH. hormone nuclear receptor (EcR) exhibits circadian cycling in certain tissues, but not others, during development in Rhodnius prolixus (Hemiptera). Cell Tissue Res 2005; 323:443-55. [PMID: 16323012 DOI: 10.1007/s00441-005-0076-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2005] [Accepted: 08/02/2005] [Indexed: 10/25/2022]
Abstract
The insect moulting hormones, viz. the ecdysteroids, regulate gene expression during development by binding to an intracellular protein, the ecdysteroid receptor (EcR). In the insect Rhodnius prolixus, circulating levels of ecdysteroids exhibit a robust circadian rhythm. This paper demonstrates associated circadian rhythms in the abundance and distribution of EcR in several major target tissues of ecdysteroids, but not in others. Quantitative analysis of immunofluorescence images obtained by confocal laser-scanning microscopy following the use of anti-EcR has revealed a marked daily rhythm in the nuclear abundance of EcR in cells of the abdominal epidermis, brain, fat body, oenocytes and rectal epithelium of Rhodnius. This EcR rhythm is synchronous with the rhythm of circulating hormone levels. It free-runs in continuous darkness for several cycles, showing that EcR nuclear abundance is under circadian control. Circadian control of a nuclear receptor has not been shown previously in any animal. We infer that the above cell types detect and respond to the temporal signals in the rhythmic ecdysteroid titre. In several cell types, the rhythm in cytoplasmic EcR peaks several hours prior to the EcR peak in the nucleus each day, thereby implying a daily migration of EcR from the cytoplasm to the nucleus. This finding shows that EcR is not a constitutive nuclear receptor, as has previously been assumed. In the brain, rhythmic nuclear EcR has been found in peptidergic neurosecretory cells, indicating a potential pathway for feedback regulation of the neuroendocrine system by ecdysteroids, and also in regions containing circadian clock neurons, suggesting that the circadian timing system in the brain is also sensitive to rhythmic ecdysteroid signals.
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Affiliation(s)
- Xanthe Vafopoulou
- Department of Biology, York University, 4700 Keele St, Toronto, Ontario, M3J 1P3, Canada.
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Kao CC, Green S, Stein B, Golden SS. Diel infection of a cyanobacterium by a contractile bacteriophage. Appl Environ Microbiol 2005; 71:4276-9. [PMID: 16085814 PMCID: PMC1183273 DOI: 10.1128/aem.71.8.4276-4279.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Light was found to strongly influence the infection of a freshwater cyanobacterium (Synechococcus elongatus PCC 7942) by a contractile DNA phage named AS-1. Phage progeny production was correlated with the amount of light in the laboratory and occurred in a diel pattern under natural light. At least one effect of light on AS-1 infection is at the level of adsorption.
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Affiliation(s)
- C Cheng Kao
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA.
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Konno N, Hyodo S, Takei Y, Matsuda K, Uchiyama M. Plasma aldosterone, angiotensin II, and arginine vasotocin concentrations in the toad, Bufo marinus, following osmotic treatments. Gen Comp Endocrinol 2005; 140:86-93. [PMID: 15613270 DOI: 10.1016/j.ygcen.2004.10.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2004] [Revised: 09/22/2004] [Accepted: 10/12/2004] [Indexed: 10/26/2022]
Abstract
To clarify the physiological roles of the renin-angiotensin-aldosterone system (RAAS) and arginine vasotocin (AVT) on body fluid regulation in amphibians, we measured plasma concentrations of aldosterone (ALDO), angiotensin II (ANG II), and AVT after various osmotic challenges in the marine toad, Bufo marinus (Bufonidae). Hematocrit value (Ht) as an indicator of plasma volume, plasma osmolality and concentrations of plasma components (Na(+), Cl(-), K(+), and urea) were also measured. The toads were maintained under various osmotic treatments for 7 days. In dehydrated toads, plasma concentrations of ALDO, ANG II, AVT, and all plasma components measured were increased. In toads maintained in 300 mosmol/kg H(2)O NaCl solution, plasma osmolality, Na(+), Cl(-), urea, and plasma AVT concentrations were significantly increased, and Ht and plasma concentrations of ALDO and ANG II were significantly decreased. In toads maintained in tap water, plasma osmolality, and concentrations of Na(+) and ALDO were significantly decreased. We also estimated total body water (TBW), plasma volume (PV) using Evans Blue dye and Ht in the toads under various osmotic treatments. In dehydrated toads, TBW and PV were significantly decreased and Ht was significantly increased in comparison with those of control. In toads maintained in 300 mosmol/kg H(2)O NaCl solution, TBW and PV were significantly increased and Ht was significantly decreased in comparison with those of control. There was a significant negative correlation between Ht and PV or TBW. These results show that dehydration, which induces hypovolemic and hyperosmotic conditions, stimulates increases of plasma ALDO, ANG II, and AVT concentrations, while hypervolemic treatment induces decreases of plasma ALDO and ANG II concentrations. There were significant correlations between plasma osmolality and AVT concentration, between Ht and concentrations of RAAS hormones, and between plasma concentrations of ALDO and ANG II. These results suggest that volumetric and osmometric systems regulated by RAAS hormones and AVT are present in B. marinus.
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Affiliation(s)
- Norifumi Konno
- Department of Biology, Faculty of Science, Toyama University, Toyama 930-8555, Japan
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Wright ML, Bruni NK. Influence of the photocycle and thermocycle on rhythms of plasma thyroxine and plasma and ocular melatonin in late metamorphic stages of the bullfrog tadpole, Rana catesbeiana. Comp Biochem Physiol A Mol Integr Physiol 2004; 139:33-40. [PMID: 15471678 DOI: 10.1016/j.cbpb.2004.06.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2004] [Revised: 06/21/2004] [Accepted: 06/21/2004] [Indexed: 10/26/2022]
Abstract
The diel fluctuations in plasma thyroxine (T(4)) and plasma and ocular melatonin entrain to the light/dark (LD) cycle in the bullfrog tadpole, although the phase of the rhythms changes during development. Previous studies on the rhythmicity of these hormones were conducted under various LD cycles, but with a constant temperature, raising the question of the role of the natural thermocycle in determining the phase of the rhythms, and the changes that occur in the hormone levels and rhythms during late metamorphosis. To study this question, tadpoles were acclimated to simulated natural conditions of 14.5L:9.5D with a corresponding thermocycle in which the thermophase was 28 degrees C and the cryophase was 18 degrees C, or to the same thermocycle under constant light (24L). On both photoregimens, the diel fluctuations changed between prometamorphosis and metamorphic climax. However, more statistically significant rhythms, as indicated by the cosinor, occurred on 14.5L:9.5D than on 24L. At climax on the LD cycle, all hormones peaked around the same time in the late scotocryophase, whereas on 24L, plasma T(4) peaked in the thermophase and plasma and ocular melatonin peaks occurred some distance from each other early in the cryophase. The earlier peaks of plasma and ocular melatonin on 24L were due to a transient rise in these hormones at the onset of the cryophase, which was not sustained in the absence of an LD cycle. On 14.5L:9.5D with a corresponding thermocycle, the hormone rhythms had nearly the same phases as was found in previous work on 12L:12D at a constant temperature of 22 degrees C, allowing for minor phase shifting due to the photocycle differences, indicating that in this species laboratory studies on constant temperature give valid results even in the absence of a thermocycle. The findings show that the phases of the hormone rhythms are determined by the LD cycle although the onset of the cryophase, in the absence of a photocycle, may exert some influence on the nighttime rise in melatonin. The developmental rise in plasma T(4), and drop in plasma melatonin, occurred on both 14.5L:9.5D and 24L, indicating, taken together with previous work, that these climactic changes were independent of temperature and light cycling.
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Affiliation(s)
- Mary L Wright
- Biology Department, College of Our Lady of the Elms, Chicopee, Massachusetts 01013, USA.
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